1. Field of the Invention
The present invention relates to a broadband transmission path apparatus of a suspension for performing signal transmission between a head IC and a head in a magnetic disk apparatus, a suspension assembly and a storage medium apparatus, and particularly to a broadband transmission path apparatus of a suspension for enabling signal transmission in a broadband beyond gigahertz, a suspension assembly and a storage medium apparatus.
2. Description of the Related Arts
Conventionally, in a magnetic disk apparatus, a head is mounted on a tip of a suspension mounted on a head actuator, and the head and a head IC mounted on the base of the actuator are electrically connected by, for example, wiring formed on a flexible printed circuit board (FPC) In recent years, there is also used a wireless suspension where a circuit layer forming a transmission path on a metal foil such as stainless through an insulator is formed by a semiconductor manufacturing process. In such a conventional magnetic disk apparatus, data in a magnetic disk medium is read by a read head using a magnetoresistive element (MR element) or the like and is input into a read amplifier incorporated in the head IC through a transmission path, and thereafter the read data is demodulated in a read channel in a control board. The conventional transmission path of the suspension for connecting the head and the head IC employs a single transmission path constituting a parallel line relative to a ground, where a transmission band is expanded by a resonant frequency generated due to a frequency characteristic of the transmission path itself and the head IC, thereby enabling transmission from DC to several hundreds MHz. There are proposed a method for changing a structure or arrangement of the transmission path in order to reduce an influence due to skin effect on the transmission path for electrically connecting the head and the head IC (Patent References 1, 2), a method for surrounding the transmission path by a shield in order to reduce an influence due to noise (Patent Reference 3), and further a method for reducing a line loss by making a hole on a metal suspension constituting a grand arranged below the transmission path through an insulator (Patent References 4, 5).    [Patent Reference 1] Japanese Patent Application Laid-Open No. 2001-162804 Publication    [Patent Reference 2] Japanese Patent Application Laid-Open No. 2002-158411 Publication    [Patent Reference 3] Japanese Patent Application Laid-Open No. 2003-204130 Publication    [Patent Reference 4] Japanese Patent Application Laid-Open No. 2003-152404 Publication    [Patent Reference 5] Japanese Patent Application Laid-Open No. 2002-251706 Publication
However, it is considered that the conventional transmission path of the suspension for connecting the head and the head IC is limited in a transmission of signals of about 1 GHz, and there is a problem that a signal no less than a transmission band of the transmission path is not transmitted at a signal transfer speed of a hard disk drive which is remarkably made faster. Further, in the method for changing the structural arrangement of the transmission path in order to reduce an influence due to skin effect in the transmission path, in the method for surrounding the transmission path by a shield in order to reduce an influence due to noise, and in the method for reducing a line loss by making a hole on a metal suspension constituting the grand arranged below the transmission path, which are conventionally proposed, there is a problem that it cannot be expected that the transmission path does not exceed the frequency band of the transmission path and that the transmission path does not function in a specific band. According to the present invention, there are provide a broadband transmission path apparatus of a suspension for enabling to transmit signals beyond about 1 GHz which is said to be a limit, a suspension assembly and a storage medium apparatus.